adam-p/markdown-here

Markdown Here is a browser extension for Chrome, Firefox, and Opera, and also an add-on for the Thunderbird email client, that lets you write emails using Markdown syntax and convert them to nicely formatted HTML before sending. Markdown is a lightweight writing syntax that uses simple characters like asterisks for bold, backticks for code, and hashes for headings, it is designed to be readable as plain text but convertible to rich HTML formatting. The problem the extension solves is that email compose boxes are rich-text editors that are clunky to use for formatting, especially for emails that include code snippets. Writing in plain text and converting is much faster. With Markdown Here installed, you write your email using Markdown syntax in the compose box, then press a hotkey or right-click and choose "Markdown Toggle", the extension instantly replaces your plain-text Markdown with properly rendered HTML that includes formatted headings, bold text, code blocks with syntax highlighting, and tables. The recipient sees the nicely formatted email. If you want to go back and edit, you can toggle it back to Markdown at any time. Beyond email, the extension also works in Google Groups posts, Blogger, Evernote, and WordPress compose interfaces. It supports LaTeX mathematical formula rendering as well. You would use Markdown Here if you frequently write technical emails containing code, documentation-style content, or structured text, and find the standard email rich-text editor awkward. It is aimed at developers and technical writers who are already comfortable with Markdown. The tech stack is JavaScript, packaged as a WebExtension compatible with Chrome, Firefox, Opera, and Thunderbird. It requires no server, all conversion happens locally in the browser.